I've been working on this a while now, so I better ask for more help.
I have a 1.3.36 Apache running in a SCO OpenServer 5.0.7 machine. Every time I do a popen I get a "NoNe SuCh=: is not an identifier" error logged. popen() still manage to return a valid handle, but with no outptut. In fact, the command doesn't get started.
I've tried several php flavors and configuration scenarios. I went from PHP 4.4.6 to 5.2.5. Still the same. I am constrained in the Apache platform, since it's been pretty hard to set a stable Apache in our platform.
The error itself is clearly a misformed environment variable definition. Indeed, phpinfo() shows a ENV["NoNe__SuCh"] ==> no value entry (note the underscores). Somehow an ill set environment gets through the PHP running process.